The present invention relates to an air leak detector and counter for use with a drainage device and more particularly to a device for indicating the elapsed time between the passage of bubbles through the underwater seal of a pleural drainage device and for indicating the total volume of air passing through the seal over a period of time.
There have been a number of prior art patents issued on pleural drainage devices utilizing underwater seals to insure that atmospheric air cannot enter the pleural cavity of the patient to which the device is connected. U.S. Pat. Nos. 3,363,626 and 3,363,627 are typical of prior art pleural drainage devices including a collection chamber, underwater seal chamber and manometer chamber. A thoracotomy tube provides a passageway to interconnect the collection chamber with the pleural cavity of a patient and an opening is provided on the other side of the underwater seal to connect the drainage device to a source of suction. In operation the water level within the manometer chamber regulates the suction from the suction source to provide the desired degree of vacuum to the collection chamber and pleural cavity of the patient. Fluids from the pleural cavity collect in the collection chamber and gases from the pleural cavity pass through the underwater seal in the form of bubbles.
Pleural drainage devices such as described above function well in maintaining the desired degree of vacuum in the pleural cavity and the underwater seal provides a means to prevent the entry of atmospheric air into the pleural cavity should, for example, the device become detached from the suction source. It has been found that the underwater seal also performs a further important function. Physicans examining the underwater seal can observe the passage of air bubbles through the seal and by monitoring the frequency of the passage of such bubbles can make a judgement as to the degree of air leak in the pleural cavity of the patient. This use of the underwater seal as a diagnostic tool is important and the present invention enhances this function so that the physician can more accurately determine the condition of the patient even though his time spent with the patient is relatively limited.
The difficulty encountered with prior art drainage devices occurs when, for example, no bubbles pass through the underwater seal or only a single bubble passes through the seal during the period of time the physican is with the patient. Under these circumstances, the physican cannot determine the time interval between bubbles nor can he estimate the total volume of air passing out from the pleural cavity of the patient over a given period of time.